DrWho

How did you go about isolating it to the driver? And when does it make the noise?

What is the legal/philosophical justification for having trial by jury in the first place? Or at least what is it they teach in law school? I think there can be shortcomings with anyone that ends up on the jury, but at the same time how much do we want our legal body to control who ends up on the jury and who doesn't? To be honest, I think I'm more concerned about ignorance than I am of poor moral character. The thing about moral character is that there is no system in the world that can prevent it, but ignorance is just plain dangerous. I think I'd rather have some people knowledgeable about the law on a jury than a jury full of idiots....especially if it was my neck on the line and I knew I was innocent.

"Tapping" a horn can be accomplished with several different methods. A "tapped horn" is not defined by a rigid construction method, and you even see variation throughout Danley's designs. The physical action of tapping provides a means to offset the acoustic mismatch of an undersized horn mouth. This allows the horn to be longer without making the system bigger. All you're doing with a tapped horn is filling in the null that happens half an octave above the Fc of the horn. This can be accomplished with the rear wave of the driver, a port, another horn passage, or it could even be accomplished with a second driver. The method is arbitrary as long as you're matching the acoustic impedance to get rid of the reflection. It's just more elegant to use a single driver than to use multiples, and the math is simpler when using the rear wave of the driver instead of adding a coupled impedance in series with the rear wave. If you pay attention to the excursion plots (or the THD profiles), you'll notice an increase in driver excursion at the frequencies where it's driving the null - and this is because the driver sees less acoustic load. However, half an octave above Fc is a better place to have that partial unloading since higher frequencies require less displacement. We can add stubs all the time in the electronics world to "tap" a transmission line - but I doubt that analogy offers any more meaning. My only point is that tapping transmission lines (of all types) is an old concept that exists in older designs. There are several other examples of scoop type bass bins where the front wave is right near the mouth of the horn, and the rear wave fires through a folded horn in the rear. The MTL1 is certainly not the only example. I'm not saying the oldschool designs were great, but it was demonstration of the principal (even if they didn't do it well).

Ya, I know....it summarizes a lot of complexity. Btw, the earliest Tapped Horn I know of was designed by the guys over at Electro-voice and it's called the MTL-1: The MTL1 has an advantage because the "reverse" taper on the horn acts like a low pass filter which removes the high frequency content from the rear path - which in turn extends the HF response. Also, I believe it was Josh Ricci who designed the Othorn and Gjallarhorn. He then designed this new MAUL to replace the Gjallarhorn. I wonder if he'll upgrade the Othorn too?

The K48 is a good driver and I enjoy the sound quite a bit. Just because I enjoy something doesn't mean I have to redefine it as "great". If it helps, I also like the sound of the Promedia 2.1 system and praise it a lot more than the Chorus II. That doesn't mean the Promedia sounds better, nor does it make the Promedia a great system. That SW152 on the other hand? It's definitely in the great driver category. Just try to find something with a higher Bl/Re rating, or more linear excursion characteristics. Maybe the vaporware Pro-5100? But then there's the IPAL version of the SW152.... All of this stuff is really about perspective. It's perfectly okay to enjoy the bargain solutions. I enjoy the bargains quite a bit. Perhaps I just have a different threshold for what I consider great. The K48 is not great in my opinion and its lack of greatness is why I've been looking for a proper alternative. I just haven't settled on one yet because I haven't found the proper the balance of compromises for my particular application.

Ain't nothing wrong with napkin drawings, but a napkin drawing certainly isn't a form of design validation - yikes! However, a plot is not just a plot. There is a reason we teach our interns and young engineers the importance of a rigorous repeatable test methodology. And my bad about the crayon....they're probably magic marker.

Eminence is a bargain basement driver supplier - you go with them because you want to increase your margins. It's the same reason Klipsch uses them. It's understandable because all that woodworking (for Danley and Klipsch) costs a lot - so you gotta take cost out elsewhere. It's totally a brilliant engineering move because you don't need as potent of a driver when you have a horn. It makes sense when you're trying to run a business and hit cost targets, etc... However, you don't run to Eminence because it will yield the best possible sound quality. It's simply not "great" stuff. Good? Adequate? Balanced compromise? Sure, absolutely. But if you're going to imply a bargain is somehow the best thing since sliced bread because your hero uses it, then you're just deluding yourself. I totally get it that several of us are cheapskates (myself included), but the money itself isn't a defining quality. Maybe it's just a personal thing, but when thinking about sound quality, the price is never a factor for me. The only thing price affects is what I personally own. It doesn't change how what I own sounds. The problem with the audiophile community is we're too elitist about what we own and want to prove to the world that we have the echelon music listening experience....and we've achieved it while spending just a few hundred dollars. To use a car analogy, I love my Elise, but I'm not naive enough to think it actually goes toe to toe with a Formula 1 car. Who cares if my fun per dollar is maximized? The Formula 1 car is still better and I don't have to piss on the Formula 1 car to enjoy my Elise.

I have a really hard time believing that....The Lab12 just isn't a great driver and I'm not sure there is any horn out there that would provide enough gain to let it keep up with the B&C 21SW152 - even if the B&C were in a sealed cabinet. Frequency response is totally the wrong plot for understanding why that is the case. I also think it's important to look at performance versus cabinet volume. Physics dictates that low frequencies need a longer horn - and that's why Klipsch doesn't market a horn sub to the home audio market. They are selling subs that are the size people want in their home. For cinema Klipsch has the 1802HLS - that would be the sub to use in the home if you want a Klipsch branded horn loaded cabinet. Why are we always subjected to these crayon drawings on graph paper for the Fitzidiot designs? Every time I see a measurement taken with industry standard software and equipment, the response plots look totally different. Btw, it looks like there is a new big boy on the market.... http://www.data-bass.com/data?page=system&id=131 Anybody know anything about this sub?

Can't we already do that?

The issue here is the moral responsibility in situations like this.....was the feature ready? How do we not have the death of an individual caused by a rushed financial pursuit? The difference about a human making the mistake is that the morality is much more clear. The thing is, the rest of the auto industry has been studying autonomy for arguably much longer than Tesla, and they've chosen a much less cavalier approach of slowly and subtly bringing in the automatic aids.

I think we read "How to kill a mockingbird" instead. I may have had a conservative arts education.....

So are you saying that if he really had balls, then he should shoot the federal game warden too? Scratches head. Uh no, not saying, suggesting or implying any malice, ill will or anything of the sort. Things rarely turn out good when you do not fully cooperate with a federal warrant except through recognized and proper channels. I'm saying any advice that suggests someone commit a federal crime, even a lowly misdemeanor, is rarely backed by common sense or reality. Haha - I think you may have missed the intense sarcasm on my part But for what it's worth, it's the intense philosophy and balanced perspectives (like you are showing here) that really causes me to respect the lawyers that I know personally. I just can't figure out how to lighten you guys up every once in a while And yes, I'm fulling anticipating a lecture on how this is serious and shouldn't be a joking matter

So are you saying that if he really had balls, then he should shoot the federal game warden too?

I love BattleBots but rarely make an intentional effort to watch it though. Back in 2007 we participated in a similar competition in college - but a lot less carnage: https://www.youtube.com/watch?v=XqcCOAiNOOU I'd love to see them add a point scoring system to BattleBots - and maybe include the carnage as part of those points. Basically make it more sport-like rather than all out brawl.

Once you're in the modal region of a room, then that kind of analysis doesn't apply. The modal region usually covers the 50Hz to 400Hz range in most rooms. We have to treat all of the reflective surfaces as multiple sources - in which case we want to approach the problem more like a line array, rather than trying to achieve a point source. The xover frequency is only adding one more additional source, and only over a very narrow range of frequencies.

Short answer is yes. However, you need to think of it in terms of bandwidth. Covering 20Hz to 80Hz is only 2 octaves. Extending that to cover 80Hz to 160Hz is 3 octaves. Your main speakers on the other hand are covering 80Hz to 20kHz. Usually your speakers are 2-way or 3-way, so really the next region of bandwidth is probably something like 80Hz to 1280Hz, which is 4 octaves. If you let them go down to 40Hz, then it's 5 octaves. So we have 2 octaves on the sub and 4 octaves for the LF section of your mains. Headroom is a bigger issue for your mains than it is for the subs. Now all that said - headroom should not be the dominant deciding factor for choosing a xover frequency. There are more variables to consider, but that's a huge topic when you start getting into it. At the end of the day, I'd recommend sticking to 80Hz for the subwoofer no matter what speakers and subs you have. It's a rare scenario where deviating from this is an advantage - and even then it's usually going to be a subtle difference. Definitely don't try going higher than 80Hz on the xover frequency unless you have multiple subs colocated with your mains.

I used to cringe about it a lot more in the past, but them crazies are doing things of great value that the cold-hearted engineering approach doesn't address. People buy into that stuff because it's the experience of it all that they're enjoying. Ya, it's often insane lunacy - but audio is the only hobby I've ever seen where the "purists" are so averse to addressing the rest of the listening experience. For example, car racing enthusiasts add stickers to their car because "it adds horsepower". If anything, the stickers make the car slower, but they don't care...the fake authenticity of looking like a real sponsored racecar makes them enjoy the racing event more. And that totally fake feeling of authenticity actually improves the mood of the drivers and then they actually drive faster. It's all part of the entire experience. The difference here is the car enthusiast crowd doesn't have such a vocal group of people crying foul about someone that chooses the fake authenticity. So instead of complaining about the snake oil insanity, I think we should be asking the "authentic solutions" to also provide the rest of the experience. Part of that experience might actually be not getting so hell bent on trying to quantify minutia that takes dozens of measurements and a college degree to understand. Btw, CEA2010 is another fun spec that is more focused on the amplitude linearity of subwoofers: http://www.audiomatica.com/wp/wp-content/uploads/appnote_007.pdf And an interesting article getting to my point about how hard it is to have absolute measures of anything: http://www.soundandvision.com/content/cea-2010-good-baseline-bass#FdPPIXRu4WYb84pW.97 Gain non-linearities as small as 0.3dB on some measurements are easily audible in blind listening tests. In others, the exact same measurement is totally inaudible. The reason is related to the mechanism that caused that non-linearity. Now go from one measurement rig to another.....those 0.3dB variations can measure quite differently - say now 0.4dB and happening slightly earlier now. Even with the same gear there will be variation - and sometimes that 0.3dB variation doesn't show up. Now I'd argue we're using the wrong measurement to identify the shortcoming of the system, but this is a common occurrence when analyzing gain / amplitude linearity. Some things are indicative of problems and other are not. When looking for an amplitude linearity spec - how then does Manufacturer A differentiate their inaudible irregularity from Manufacturer B with a much more audible problem? From a sales and marketing perspective, neither manufacturer wants to call attention to the irregularity in the first place. And if they do, then the customers get confused and start distrusting science when they realize that A sounds better than B even though they have this measurement telling them "A is worse". You seriously need about 30 incredibly accurate measurements of a system before you can really start getting a feel for how it sounds - and even then you're filling in the blanks based on your knowledge of the topology. The only clean non-technical story is to simply talk about the major design elements....like the topologies used. And that's exactly what we see in the audio industry. We talk about speakers that are hornloaded or ported, or amplifiers that are Class A or AB, etc....big picture topologies. Honestly, it matters way more than trying to throw measurements at something to understand why it sounds the way it sounds.....assuming of course it was designed properly. Granted, things often aren't designed and built properly, but that will come out in the listening anyway. At which point, do we really need measurements to tell us what our ears have already heard? The reason I'm asking these questions and pushing down this path is because it really matters why you're looking for an amplitude linearity spec.

Right, because sales and marketing is a complete waste of time and money. It's usually only the engineering types that have the right combination of arrogance and ignorance to think that engineering is the only thing that matters in this world. These same people often like to parade around using numbers to extol their subjective preferences and convince the world that they're further along than everyone else. The fact that most audio companies don't publish every single measurable parameter of a device is because it is a horrible marketing strategy! Never mind the fact that it would be confusing to even the most educated of customers. Heck, it's confusing to the most educated of engineers too! Why the heck burden a sales force with such complicated subjects? The exploration into the subjective correlation to objective measure will forever be a topic of intense research - and the experts in the field certainly are nowhere near agreement (not surprising given the subjective nature of the field). I hope you're pinning that BS Button to your shirt Chris because you're way out of your league here. The other funny thing here is the arrogant-ignorant-number-bashing-idiots talk so much about removing bias from the listening/purchasing equation. An open-minded person would realize that the "non-audible" factors when listening actually have a huge impact on the audible impressions of the person. The audiophile boutique craziness exists because that very craziness enhances the listening experience! We should be embracing those realities, and even engineering them.....not running around beating our chests about how we're free from the vices of aesthetics and a proper human purchasing experience. The sales / business types totally understand this - the engineers are too proud to admit it. None of that changes what measurements do tell us, but to get on this kick that somehow we can quantify the human experience is simply childish. Btw, I do absolutely conduct listening tests where we try our best to remove the bias factor. It's very important in the design world to isolate the objective impact of a single variable. However, it's equally important to conduct the same listening tests when bias is a factor. Music is art, not documentation.

That kind of analysis works for really large artifacts, but for smaller artifacts (like what we get in electronics world) we should use gain linearity to show the minor differences. Page 22 in the attachment starts talking about non-linearity, and Page 26 has a graph of what I'm referring to. Of course this can be used in speaker world too. I think analyzing distortion numbers is too complicated for engineers too. These types of analysis are invaluable for verifying designs, but they don't tell you a lot about how they're going to sound. The design decision that creates the artifacts that shows up in the measurements are what dictate the audible result. The measurements are just tools to make sure the shortcomings of a particular topology are minimized. In other words, the true art in audio design is in the architecture and selection of topologies. For a given topology, if two designs are implemented well, then they are going to sound very similar. By extension, the consumer really doesn't need to get bogged down in the technical detail. Find the topology you like, and choose a company that you trust to implement it well. Trying to find a holistic unit of measure to compare every possible typology is kinda ignoring the original purpose of measuring in the first place.....we don't use measurements to understand how something sounds. We listen with our ears to understand how something sounds. We use measurements to fix (audible) problems... AMH-1.pdf

How would you quantify it? Do you look at distortion versus SPL? Gain linearity versus SPL? What frequencies, and what amplitudes do you measure? What kinds of distortion? Do you use perceptual weightings on the results? Are there minimum noise/distortion targets too?

Here is the equation I use for a conical horn: https://www.grc.com/acoustics/an-introduction-to-horn-theory.pdf St and Xo are independent free variables and cannot be consolidated outside the brackets. Regardless, the conical equation is not applicable here because it only predicts total power transfer, and the assumptions behind it don't hold true in nature. Although we gain some insight from equations like the conical, they still don't accurately describe the real world behavior.

Not to get too far down a rabbit trail, but I wonder if the total efficiency of the system is really the variable we're trying to optimize....and what I mean by that is efficiency calculated as Electrical Power delivered by the amplifier divided by the acoustic output power. This is what Beranek is calculating (if we're thinking the same equation). The reason I say that is because the electrical output power of the amplifier doesn't dominate the distortion of the entire system. It seems like the dominant distortions are driven by the motion of the mechanical components, like the suspension, diaphragm, motor, and even the air. The power dissipating of the driver usually doesn't matter either - certainly not in a home environment. What if we had a system where the electrical input power requirements were higher, but the cone excursion was less for the same SPL? In other words, I think we want to maximize the mechanical efficiency of the system....basically looking at cone excursion versus acoustic output. In hornresp, you can see what I'm talking about by running a MaxSPL calculation. Enter the specs for a fake driver that has very little cone excursion, but a crap ton of electrical power and you'll see a red line indicating excursion limited output. It's really only at the high frequencies where power handling is the limiting factor, but size of the horn isn't as limiting for the HF as it is for the LF. So all that to say.....do you see an increase or decrease in cone excursion when you decrease the compression ratio? Efficiency may be higher, but what is happening to the total distortion of the system? Maybe the larger throat has less distortion? Beranek gives us some calculations for that too (just to get an idea for order of magnitude).

Double post.

I'd say for sure the breakup is getting into the 400Hz region, but I'm not sure how much lower it goes. Maybe another octave? As you go lower, cone excursion increases so at the lowest octaves I think the motor linearity probably dominates. I think a lot of these systems are using overhung coils and weaker sauce magnets. Here's a dude talking about AlNiCo mojo: http://www.tedweber.com/lets-talk-speakers/ "The whole 'AlNiCo mojo' is about smooth compression at high average levels, such as what you would have running the amp flat out. AlNiCo (Aluminum-Nickel-Cobalt) is an alloy magnet and all alloy magnets are easier to demagnetize than comparable Ceramic (Strontium Ferrite) magnets. What this means is that as the voice coil starts moving in response to the input signal, it generates a magnetic field of its own that tries to demagnetize the magnet. As its effect lowers the available magnetic field of the AlNiCo magnet, the speaker becomes less efficient, the voice coil moves less, etc. The physics of it is that the small magnets near the surface of the magnet poles (called 'domains') begin to change state, or flip directions. The result is smooth compression, the same kind of operating curve compression that occurs in a tube amplifier."

I would think you'd want the guitar cab distortion to be as broadband as possible so that it doesn't sound "one-notey" in its timbre. Maybe I could get around to measuring distortion of the various guitar cabs I have access to. I've always been curious about what it looks like. I too have never seen anything quantifying that kind of performance.... Actually, I was talking with my coworkers while writing this and they mentioned having seen some studies. We're in China watching the paint dry as we bring up all our manufacturing and test fixtures. Anyways, here's an interesting article: http://legacy.spa.aalto.fi/dafx08/papers/dafx08_17.pdf The last page shows a good distortion summary - the rest of the article took me a bit to wrap my head around. I think one of the interesting things they were exploring is the corrugation on the cone and the frequency specific velocity at each point. Or here's a more human readable article: http://www.soundonsound.com/sos/feb12/articles/speakers.htm And an interesting quote from Ian White (of Celestion): "Designing guitar speakers is, in many ways, much more challenging than pro PA or hi-fi, because guitar speakers are so non-linear,” he says. "Hi-fi speakers are designed for linear operation mainly within what's called their 'pistonic band', the region where the speaker is moving in and out in linear fashion. Above that band, the speaker goes into 'break-up' — instead of the whole thing acting coherently like a pump or piston, little bits of the cone are all doing their own thing — but then you'd typically move that part of the signal over to, say, a mid-range driver or tweeter. With guitar speakers, there's almost no pistonic band. Within their usable frequency range, it's almost all break-up.” and "The effect of signal level is not huge,” says Ian White, "and certainly not as big as it is on the amplifier. These cone break-up mechanisms happen at a few microvolts input. You don't need to drive 20 Volts into the thing to make them happen. There are some level-related effects that come into play, but they're not the ones we've been talking about up to now. It seems to me like the idea of pistonic motion is completely thrown out the window with these drivers? Obviously these are broad brush strokes so maybe there are exceptions to the trend? I dunno. I just know when I was designing my own bass guitar cabinets that we didn't like the sound of the ultra linear hi-fi drivers. We ended up going with an aluminum diaphragm Eminence driver because it had the sound my buddy was going for....really crisp because of how the aluminum would distort. The paper drivers couldn't give us that level of crispness and still have the bottom end we were looking for (he played a five string).